Biologically degradable polymer mixture

ABSTRACT

A biologically degradable polymer mixture contains at least one starch biopolymer made from renewable raw materials, a plasticizer, and a polymer selected from the following materials: an aromatic polyester; a polyester-copolymer with both aliphatic and aromatic blocks; a polyesteramide; a polyglycol; a polyester urethane; and/or mixtures of these components.

The present invention relates to a biologically degradable polymermixture, to a process for its preparation and to a method of processingthe polymer mixture according to the invention.

Proposals for the preparation of biologically degradable polymermixtures are known from a large number of patent documents and articles.The great problem in the case of polymer mixtures lies, as a rule, inthat those mixtures which have an excellent, biological degradabilityhave only limited possibilities for use in the area of engineeringplastics, thereby explaining the relatively modest success to date.Polymer mixtures having improved properties are either biologicallyinadequate or degradable with increased effort, or else are tooexpensive.

From EP-535 994 a polymer mixture is known essentially consisting ofstarch and an aliphatic polyester, for example polycaprolactone, wherethe starch is preferably destructured with water.

Aliphatic polyesters are, per se, suitable mixing components for thepreparation of biologically degradable polymer mixtures, since they havea good biological degradability. However, aliphatic polyesters have onlymoderate material properties, for example with regard to melting point,tensile strength, etc., which is why even corresponding mixtures using apolymer prepared on the basis of renewable raw materials, for examplethermoplastic starch, have only moderate properties, thereby againplacing in question the possibility for use in the field of engineeringplastics.

It is therefore an object of the present invention to propose abiologically degradable polymer mixture which both is flawlesslydegradable biologically and in addition has good mechanical and thermalproperties, so that use as an engineering plastic or as a polymermaterial is appropriate. A further prerequisite for suitability as apolymer material also lies in the price for the polymer mixture proposedhaving an acceptable magnitude.

The multitude of biopolymers or biologically degradable polymer mixturesproposed in the prior art are to a great extent in accordance withobject having an acceptable magnitude.

In accordance with the invention the object proposed above is achievedby means of a biologically degradable polymer mixture in accordance withthe wording of claim 1.

The multitude of biopolymers or biologically degradable polymer mixturesproposed in the prior art are to a great extent constructed on the basisof starch or use starch, although native starch is hardly suitable as atechnically usable polymer. Starch is proposed because it is readilydegradable biologically, has a favorable price and is independent ofpetroleum products because it is based on a renewable raw material.Because of the poor suitability of native starch as an "engineeringplastic" it is proposed according to the invention to use so-calledthermoplastic starch, as is proposed, for example, in PCT/WO90/05161.This thermoplastic starch is obtained by processing native starch in themelt, by means of a plasticizing or swelling agent, to a homogeneousmass, where the proportion of swelling or plasticizing agent can as arule amount to between 10 and about 40%, based on the overall weight ofthe mixture. [As set out in claim 4,] Suitable swelling or plasticizingagents are, inter alia, for example, glycerol or sorbitol.

Particularly suitable materials for improving the rather moderatematerial properties of thermoplastic starch include:

The aliphatic polyesters proposed in the prior art, which althoughhaving good biological degradability are not particularly suitablebecause of their likewise moderate material properties with regard tomelting point and drawability, themselves contribute to an improvementin the material properties of the thermoplastic starch. In contrast,aromatic polyesters exhibit excellent material properties but theirbiological degradability is rather moderate. On the other hand, interalia, polyester copolymers based on aromatic and aliphatic dicarboxylicacids, polyesteramides and also polyesterurethanes have both outstandingmaterial properties and a rapid biological degradability, which is whythey are particularly suitable for use in polymer mixtures withthermoplastic starch.

The polyester copolymers proposed for use in accordance with theinvention in the polymer mixture with thermoplastic starch areconstructed on the basis, besides the customarily used polyols, ofaromatic and aliphatic dicarboxylic acids, and have the followinggeneral structure: ##STR1##

The polyester copolymers proposed according to the invention can beprepared from petrochemical mass products, such as adipic acid, sebacicacid, terephthalic acid and a diol by means of polycondensation, withcommercially customary diols, such as 1,2-ethanediol, 1,3-propanediol,1,4-butanediol and/or 1,6-hexanediol being used. What is important isthat both aromatic and aliphatic dicarboxylic acids are used, by meansof which the statistical polyester copolymers are prepared, for exampleby means of a conventional polycondensation process.

Statistical copolyesters of aliphatic and aromatic dicarboxylic acidswith a proportion, for example, of about 35-55 mol % of aromatic acid,for example terephthalic acid, represent an optimum compromise betweenbiological degradability and material properties, as a result of whichthey are particularly suitable in mixtures with thermoplastic starch.The biological degradability of statistical copolyesters of this kindlies within 8-12 weeks in compost and earth. In this context referencemay be made to U.S. Pat. No. 5,446,079, in which the preparation ofaliphatic-aromatic copolyesters is described in detail.

Polyalkylene terephthalates and polyethylene terephthalates which areprepared from aliphatic diols and aromatic dicarboxylic acids haveproven, for example, to be suitable copolyesters for the preparation ofa starch/polyester copolymer blend according to the invention.

In addition to the starch/polyester copolymer blends described above andproposed according to the invention it has become evident thatpolyesteramides filled or blended with starch or thermoplastic starchand with ester contents of between 30 and 70% by weight have goodmechanical properties, even for the production of films, and have gooddegradability and compostibility. Proposed are, for example,polyesteramides having a mean molecular weight in a range of 10-300,000,preferably 20-150,000. Otherwise reference may be made to the Europeanpatent application EP-A-641 817, in which the synthesis of thepolyesteramides proposed in accordance with the invention is describedin detail. Mention should merely be made that polyesteramides accordingto the invention can be constructed from monomers of the followinggroups:

dialcohols, such as ethylene glycol, 1,4-butanediol, 1,3-propanediol,1,6-hexanediol diethylene glycol and others; and/or

dicarboxylic acid, such as oxalic acid, succinic acid, adipic acid andothers, including those in the form of their respective esters (methyl,ethyl etc.); and/or

hydroxycarboxylic acids and lactones, such as caprolactone and others;and/or

amino alcohols, such as ethanolamine, propanolamine etc.; and/or

cyclic lactams, such as E-caprolactam or laurolactam etc.; and/or

ω-aminocarboxylic acids, such as aminocaproic acid etc.: and/or

mixtures (1:1 salts) of dicarboxylic acids such as adipic acid, succinicacid etc. and diamines such as hexamethylenediamine, diaminobutane etc.

In the case where the polymer mixture is based extensively onthermoplastic starch and an aromatic polyester, an aliphatic-aromaticcopolyester or a polyesteramide it may be advantageous to add analiphatic polyester or copolyester, such as polycaprolactone, forexample, as a further component. By this means the relatively poorbiological degradability, for example, of the aromatic polyester iscompensated by the excellent degradability of the aliphatic polyester.As an example of this there may be mentioned a polymer mixtureconsisting of thermoplastic starch, at least one polyethyleneterephthalate (PET) or a polyalkylene terephthalate, andpolycaprolactone. Other examples of aliphatic polyesters or copolyestersare polylactic acid, polyhydroxybutyric acid, polyhyroxybenzoic acid,polyhydroxybutyric acid-hydroxy-valeric acid copolymer and/or mixturesthereof.

Depending on how the preparation of the polymer mixture is carried outit is advantageous if this mixture additionally contains a blockcopolymer as phase mediator in order to form a continuous, homogeneousphase between the thermoplastic starch and the hydrophobic polymer inthe form of the polyester. A phase mediator of this kind can, forexample, be a reaction mixture obtained by essentially anhydrous mixingof thermoplastic starch or, if desired, native or destructured starchwith an aliphatic or aromatic polyester or copolyester, with anaromatic/aliphatic copolyester, with a polyesteramide and/or apolyesterurethane.

The proportion of thermoplastic starch containing the above-mentionedplasticizing or swelling agent can make up a proportion of between10-95% by weight, based on the overall weight, in the polymer mixtureproposed in accordance with the invention; preferably, 30-75% by weightof thermoplastic starch is used. The proportion of thermoplastic starchdepends on the one hand on the polyester or copolyester used and on theother hand on the intended use of the polymer mixture, such as injectionmolding, extrusion or film blowing. The requirements with regard to thematerial properties also influence the proportion of thermoplasticstarch. If, for example, heightened material requirements with respectto mechanical and thermal properties are imposed, a proportion ofthermoplastic starch in the range of 40-65% by weight will preferably betargeted; consequently, the price of the mixture remains acceptable inany case.

Also a subject of the present invention are mixtures containing 90-30,especially 80-40% by weight of thermo-plastically processiblepolyesteramides comprising 30-70% by weight aliphatic esters and 70-30%by weight aliphatic amide structures, where, furthermore, preferably10-90% by weight, in particular 20-60% by weight of starch orthermoplastic starch are contained.

The addition of further additives, such as plasticizers, stabilizers,antiflaming agents and also further, biologically degradable polymers,such as cellulose esters, cellulose acetate, cellulose,polyhydroxybutyric acid, hydrophobic proteins, polyvinyl alcohol, etc.,is possible and again is guided by the requirements with regard to thepolymer mixture to be prepared and of course also by the availability ofthe corresponding components. The polymers indicated below are alsosuitable as additives, such as gelatins, proteins, zeins,polysaccharides, cellulose derivatives, polylactides, polyvinyl alcohol,polyvinyl acetate, polyacrylates, sugar alcohols, shellac, casein, fattyacid derivatives, plant fibers, lecithin, chitosan,polyesterpolyurethanes and polyesteramides. Mention should also be madeof polyester blends consisting of thermoplastic starch, thealiphatic/aromatic polyester proposed according to the invention and, asfurther component, copolymers selected from ethylene-acrylic acidcopolymer and ethylene-vinyl alcohol copolymer.

Also suitable as fillers are, in particular, organic fillers obtainedfrom renewable raw materials, for example cellulose fibers.

In order to reduce the hydrophilic polymer properties of materialscomprising thermoplastic starch it is also possible to add crosslinkingagents, for example alkylketene dimers of the following general formula:##STR2## where R=linearly saturated alkyl group in the range fromC12-C24. The concentration of such network agents amounts as a rule toabout 0.05-2%, based on the weight, proportion of dry thermoplasticstarch in the polymer mixture, preferably 0.1-1% by weight. The proposedalkylketene dimers react in this case with the hydroxyl groups of thestarch polymer.

The preparation of the polymer mixture proposed according to theinvention takes place by mixing starch, such as preferably thermoplasticstarch, together with the aromatic polyester and/or the polyestercopolymer containing aromatic and aliphatic constituents in the melt,the water content in the mixture being reduced before or during mixingto less than 1% by weight, based on the weight of the mixture.

Especially in the case of the exclusive use of an aromatic polyestertogether with the thermoplastic starch for the preparation of thepolymer mixture it has proven advantageous to add, in addition, analiphatic polyester during the preparation. Examples of suitablealiphatic polyesters are, for example, polycaprolactone, polylacticacid, etc., as already set out above. Further suitable aliphaticpolyesters are, for example, polyethylene succinate (PESU) andpolybutylene succinate (PBSU). The latter aliphatic polyesters areformed by reaction of glycols with aliphatic dicarboxylic acids andother acids and have the following general structural formula: ##STR3##

In every case it is proposed, in accordance with a preferred variantembodiment of the process according to the invention, to reduce thewater content during the mixing of the melt to below 0.5% by weight,preferably even to below 0.1% by weight, based on the overall weight ofthe mixture.

In the preparation of the polymer mixture proposed in accordance withthe invention, the thermoplastic starch is present to begin with as aso-called disperse phase, while the polyester or the copolyester, thepolyesteramide or the polyesterurethane, representing a hydrophobicpolymer, is present as a substantially coherent, continuous phase. Anobvious supposition, then, is that when the two polymers are mixed withthe exclusion of water the ester groups incorporated in the moleculechains of the polyester or copolyester, etc. undergo esterificationreactions with the thermoplastic starch, as a result of which themolecule chains reacting in this way form a phase mediator with thestarch which allows a molecular coupling of the two phases, andconsequently a continuous phase is formed. In the case of moisture thisreaction is in competition, since in the presence of water the acidester groups do not react with the starch, to form the phase mediator,but instead are hydrolyzed. This, however, prevents formation of thephase mediator, which renders flawless dispersing or homogenizingimpossible. It is of course possible to use a phase mediator from theoutset, such as a block copolymer which comprises at least two blocks,one block being at least substantially soluble in the hydrophobicpolyester phase and the other block being at least substantially solublein the starch phase. In this context reference may be made to DE-42 37535.5.

Depending on the aromatic, aliphatic, aromatic/aliphatic copolyesterpolyesteramide and/or polyesterurethane used, mixing is conducted in themelt in a temperature range between 120-260° C., preferably in a rangeof 140-160° C. The mixing temperature must be chosen so that no damagecan occur to the polyester or copolyester used. The mixing of thethermoplastic starch with the polyester component or components,together if desired with further additives and components, takes placepreferably in an extruder or kneader, which preferably has adevolatilizing device, for the continuous removal of moisture, in orderto attain the required freedom from water. It has been found that, whenthe thermoplastic starch is mixed with the polyester or polyesters,water is formed, which allows one to draw the conclusion of, forexample, the above-mentioned reaction of the ester groups with thestarch to form the phase mediator. On leaving the extruder or kneaderthrough the die the melt has an extremely low water content, preferably<0.5 or <0.1% by weight. After removal from the die the melt ispreferably cooled in a water bath and conditioned before being subjectedsubsequently granulated, for example. It has proven advantageous if themelt, which is dry per se, is cooled in a water bath so that it absorbswithin the order of magnitude of 2--about 6% by weight, based on theoverall weight, of water, in order to ensure flawless granulation.

The polymer mixture prepared in accordance with the invention,comprising at least thermoplastic starch and, for example, the polyestercopolymer comprising aromatic and aliphatic blocks, is outstandinglysuitable as a polymer material for a very wide variety of applicationsin the field of so-called "engineering plastics". Processing in theinjection molding process, as well as by extrusion and film blowing, ispossible, for instance. However, when processing the polymer mixtureaccording to the invention it has been found advantageous if the polymermixture, which is present for example as granules, is conditioned beforeprocessing, either by means of water or with a plasticizer, such asglycerol or a mixture thereof. The target is, for example, a watercontent of about 1-6% by weight, based on the overall weight, preferably3-5% by weight, as is usual, for example, in the processing ofpolyesters. Also, the injection moldings, extrudates or films producedare preferably stored directly after their preparation in an environmenthaving a relative humidity of at least 40%, preferably at least 45-50%.

Examples of possible and preferred polymer mixtures, exhibiting at leaststarch or thermoplastic starch and a hydrophobic polymer as claimed inone of the dependent claims 2-15 or prepared in accordance with aprocess set out in one of claims 16-22 are listed in Tables 1-4 depictedbelow. These examples are supplemented by an additional experiment 29.

The total of 29 examples indicated in this case include both componentswhich have been used for the preparation of thermoplastic starch in thesense of plasticizing agents or swelling agents and the possiblepolymeric mixing partners to the thermoplastic starch for thepreparation of the polymer mixtures proposed in accordance with theinvention. The tables include, moreover, the processing conditions and,in particular, the water content in the extruder which prevails duringthe preparation of the polymer mixture, and which without exceptionamounted to <than 0.1% by weight. In addition, preferred applicationoptions for the polymer mixtures prepared by way of example are set outin the tables. The tables of course contain only examples, and allcomponents mentioned at the outset are suitable for mixing with starchor thermoplastic starch for preparing starting polymer mixtures, definedin accordance with the invention, for both technical and nontechnicalapplications.

                                      TABLE 1                                     __________________________________________________________________________    Examples                                                                      Example                                                                              1    2   3    4   5    6   7                                           __________________________________________________________________________    .sup.1 Starch %                                                                      42.2 24.0                                                                              29.9 24.0                                                                              33.0 38.0                                                                              21.5                                        .sup.1 Sorbitol %                                                                    14.0 8.0 9.5  8.0 9.9  11.8                                                                              6.9                                         .sup.1 Glycerol %                                                                    9.5  6.0 6.5  6.0 7.9  9.3 2.1                                         .sup.2 TPS %                                                                         60.5 34.9                                                                              42.0 34.9                                                                              46.7 54.5                                                                              27.8                                        H.sub.2 O %                                                                          <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1                                        .sup.3 PLA %                                                                         --   --  --   --  40.0 10.9                                                                              --                                          .sup.4 Polyamide 1                                                                   34.3 50.0                                                                              --   --  9.2  --  69.5                                        .sup.5 Polyester 1                                                                   --   --  54.1 45.0                                                                              --   30.0                                                                              --                                          .sup.6 PCL %                                                                         --   12.0                                                                              --   17.0                                                                              --   --  --                                          H.sub.2 O %                                                                          <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1                                        .sup.7 Extrusion                                                                     ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                      T ° C.                                                                        212  225 210  210 215  210 200                                         Pressure bar                                                                         8.5  2.0 2.5  2.5 6.2  7.5 0.5                                         MFI g/10'                                                                            9    13  11.5 13  8.5  8.0 29                                          Granules                                                                             4 mm 4 mm                                                                              4 mm 4 mm                                                                              4 mm 4 mm                                                                              4 mm                                        Gra H.sub.2 O %                                                                      3.0  3.6 3.4  3.6 3.4  3.4 3.0                                         Application                                                                   Blown film                                                                           +    +   +    +   +    +   -                                           Flat film                                                                            +    +   +    +   +    +   -                                           Sheets +    +   +    +   +    +   -                                           Injection                                                                            +    -   -    -   -    -   -                                           molding                                                                       Fibers -    +   -    +   -    -   +                                           __________________________________________________________________________     .sup.1 Starch = native potato starch dried 3.5% H.sub.2 O, sorbitol =         sorbitol LG DHR 71%, glycerol 99.5%;                                          .sup.2 TPS = thermoplastic starch = starch + sorbitol + glycerol < 0.1%       H.sub.2 O. -- Water content by devolatilization, according to the known       process EP 0 397 819 anhydrous TPS consists of starch, sorbitol and           glycerol;                                                                     .sup.3 PLA (polylactic acid resin) -- Mitsui Toatsu Chemicals LACEA H 100     MFR 13 190° C. 2.16 kg:                                                .sup.4 Polyamide 1 = Bayer BAK 1095 polyersteramide MFI 2.5 150° C     2.16 kg;                                                                      .sup.5 Polyester 1 = BASF ZK 242/108 copolyester of aliphatic diols and       aliphatic/aromatic dicarboxylic acids MVR 3.0 at 190° C./2.16 kg;      .sup.6 PCL (polycaprolactone) + Union Carbide Tone Polymer P787 MFI 1.0       125° C. 44 psi g/10 min;                                               .sup.7 Extrusion Equipment = Werner & Pfleiderer ZSK 40;                      *0.1-0.4% water content                                                  

                                      TABLE 2                                     __________________________________________________________________________    Examples                                                                      Example                                                                              8    9   10   11  12   13  14                                          __________________________________________________________________________    .sup.1 Starch %                                                                      38.2 24.6                                                                              29.2 24.6                                                                              30.7 28.0                                                                              21.5                                        .sup.1 Sorbitol %                                                                    12.8 8.2 9.4  8.8 9.1  8.8 6.9                                         .sup.1 Glycerol %                                                                    8.5  6.0 6.2  6.0 7.4  6.2 4.1                                         .sup.2 TPS %                                                                         54.5 35.5                                                                              41.1 36.0                                                                              43.5 39.5                                                                              29.7                                        H.sub.2 O %                                                                          <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1                                        .sup.3 PPDX %                                                                        34.0 --  --   6.5 --   --  33.8                                        .sup.4 PT-C300                                                                       --   --  45.1 --  --   --  --                                          .sup.5 PT-T8-200                                                                     --   32.5                                                                              --   --  47.0 57.0                                                                              --                                          .sup.6 BAK                                                                           6.5  28.7                                                                              10.1 54.1                                                                              5.8  --  33.7                                        H.sub.2 O %                                                                          <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1                                        .sup.7 Extrusion                                                                     ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                      T ° C.                                                                        220  214 240  215 215  210 205                                         Pressure bar                                                                         6.5  3.5 5.5  7.5 4.5  7.5 0.5                                         MFI g/10'                                                                            8    13  2.5  11.5                                                                              8.5  8.0 30                                          Granules                                                                             4 mm 4 mm                                                                              4 mm 4 mm                                                                              4 mm 4 mm                                                                              4 mm                                        Gra H.sub.2 O %                                                                      3.9  3.6 3.5  3.3 3.4  3.6 3.2                                         Application                                                                   Blown film                                                                           +    +   +    +   +    +   -                                           Flat film                                                                            +    +   +    +   +    +   -                                           Sheets +    +   +    +   +    +   -                                           Injection                                                                            +    -   +    -   -    -   -                                           molding                                                                              <0.15*   <0.4*                                                         Fibers -    -   -    -   -    -   +                                           __________________________________________________________________________     .sup.1 Starch = native potato starch dried 3.5% H.sub.2 O, sorbitol =         sorbitol LG DHR 71%, glycerol 99.5%;                                          .sup.2 TPS = thermoplastic starch = starch + sorbitol + glycerol < 0.1%       H.sub.2 O. -- Water content by devolatilization, according to the known       process EP 0 397 819 anhydrous TPS consists of starch, sorbitol and           glycerol;                                                                     .sup.3 PPDX. Polyparadioxanone. Shell International Chemicals Ltd. peak       melting deg ° C. 110.;                                                 .sup.4 PTC300ZT. Enviro Plastic, Plantet Polymers, VICAT Softening Temp.      89° C. Polyethylene oxide polymers;                                    .sup.5 PTT8-200DL. EnviroPlastic C. Planet Polymers, Polyethylene oxide       polymers;                                                                     .sup.6 Polyesteramide BAK 1095, Bayer AG, MFI 2.5 150° C., 2.16 kg     .sup.7 Extrusion Equipment = Werner & Pfleiderer ZSK 40;                      *0.1-0.4% water content                                                  

                                      TABLE 3                                     __________________________________________________________________________    Examples                                                                      Example                                                                              15   16  17   18  19   20  21                                          __________________________________________________________________________    .sup.1 Starch %                                                                      20.9 24.6                                                                              20.4 24.6                                                                              9.2  9.2 9.2                                         .sup.1 Sorbitol %                                                                    7.0  8.2 6.6  8.8 2.7  2.7 2.7                                         .sup.1 Glycerol %                                                                    4.7  6.0 4.4  6.0 2.2  2.2 2.2                                         .sup.2 TPS %                                                                         29.9 35.5                                                                              28.6 36.0                                                                              13.0 13.0                                                                              13.0                                        H.sub.2 O %                                                                          <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1                                        .sup.3 Filler %                                                                      26.9 --  25.0 --  60.0 --  60.0                                        .sup.4 Polyamide 1                                                                   40.5 36.2                                                                              --   --  25.9 27.9                                                                              --                                          .sup.5 Polyester 1                                                                   --   --  43.6 35.6                                                                              --   --  25.9                                        .sup.6 Filler %                                                                      --   25.0                                                                              --   25.0                                                                              --   58.0                                                                              --                                          H.sub.2 O %                                                                          <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1                                        .sup.7 Extrusion                                                                     ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                      T ° C.                                                                        203  206 220  21S 205  20S 220                                         Pressure bar                                                                         156.5                                                                              21  15   22  3S   40  35                                          MFI g/10'                                                                            13   9   12.5 8.5 3    2.8 2.2                                         Granules                                                                             4 mm 4 mm                                                                              4 mm 4 mm                                                                              4 mm 4 mm                                                                              4 mm                                        Gra H.sub.2 O %                                                                      3.5  3.6 3.4  3.6 3.4  3.4 3.0                                         Application                                                                   Blown film                                                                           -    -   -    -   -    -   -                                           Flat film                                                                            (+)  (+) (+)  (+) -    -   -                                           Sheets +    +   +    +   +    +   +                                           Injection                                                                            +    +   +    +   +    +   +                                           molding                                                                              <0.2%*                                                                             <0.2%*                                                                            <0.2%*                                                                             <0.2%*                                                                            <0.2%*                                                                             <0.2%*                                                                            <0.2%*                                      Fibers -    -   -    -   -    -   -                                           __________________________________________________________________________     .sup.1 Starch = native potato starch dried 3.5% H.sub.2 O, sorbitol =         sorbitol LG DHR 71%, glycerol 99.5%;                                          .sup.2 TPS = thermoplastic starch = starch + sorbitol + glycerol < 0.1%       H.sub.2 O. -- Water content by devolatilization, according to the known       process EP 0 397 819 anhydrous TPS consists of starch, sorbitol and           glycerol;                                                                     .sup.3 Filler, microized cellulose;                                           .sup.4 Polyamide 1 = Bayer BAK 1095 polyersteramide MFI 2.5 150° C     2.16 kg;                                                                      .sup.5 Polyester 1 = BASF ZK 242/108 copolyester of aliphatic diols and       aliphatic/aromatic dicarboxylic acids MVR 3.0 at 190° C./2.16 kg;      .sup.6 Filler, micronized cotton                                              .sup.7 Extrusion Equipment = Werner & Pfleiderer ZSK 40;                      *0.1-0.4% water content                                                  

                                      TABLE 4                                     __________________________________________________________________________    Examples                                                                      Example                                                                              22   23  24   25  26   27**                                                                              28**                                        __________________________________________________________________________    .sup.1 Starch %                                                                      34.5 35.5                                                                              40.5 50.5                                                                              60.7 70.3                                                                              67.8                                        .sup.1 Sorbitol %                                                                    --   --  --   --  --   --  --                                          .sup.1 Glycerol %                                                                    16.3 16.5                                                                              12.0 7.1 4.0  4.5 --                                          .sup.2 Polyamide 1                                                                   25.0 23.5                                                                              47.5 42.4                                                                              35.3 25.2                                                                              32.2                                        .sup.3 TPS %                                                                         74.8 74.4                                                                              98.6 98.5                                                                              98.2 87.4                                                                              87.8                                        H.sub.2 O %                                                                          <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1                                        .sup.4 PLA %                                                                         24.2 --  --   --  --   --  --                                          .sup.5 Polyester 1                                                                   --   24.5                                                                              --   --  --   --  --                                          .sup.6 --   --  --   --  --   --  --                                          H.sub.2 O %                                                                          <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1 <0.1                                                                              <0.1                                        .sup.7 Extrusion                                                                     ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                                                             ZSK 40                                                                            ZSK 40                                      T ° C.                                                                        200  206 190  170 160  155 155                                         Pressure bar                                                                         15   15  20   26  31   35  37                                          MFI g/10'                                                                            12   14  122.5                                                                              10  6    5   5.5                                         Granules                                                                             4 mm 4 mm                                                                              4 mm 4 mm                                                                              4 mm 4 mm                                                                              4 mm                                        Gra H.sub.2 O %                                                                      2.1  2.1 2.2  2.6 0.4  0.4 0.3                                         Application                                                                   Blown film                                                                           +    +   +    +   +    +   +                                           Flat film                                                                            +    +   +    +   +    +   +                                           Sheets +    +   +    +   +    +   +                                           Injection                                                                            -    -   -    (+) +    +   +                                           molding                  <0.15%*                                                                            <0.2%*                                                                            <0.2%*                                      Fibers -    -   -    -   -    -   -                                           __________________________________________________________________________     .sup.1 Starch = native potato starch dried 3.5% H.sub.2 O, sorbitol =         sorbitol LG DHR 71%, glycerol 99.5%;                                          .sup.4 Polyamide 1 = Bayer BAK 1095 polyersteramide MFI 2.5 150° C     2.16 kg, function of plasticizer;                                             .sup.2 TPS = thermoplastic starch = starch + sorbitol + glycerol and/or       BAK 1095, <0.1% H.sub.2 O. -- Water content by devolatilization, accordin     to the known process EP 0 397 819. 27** + 28** starch = native potato         starch, 18% H.sub.2 O:                                                        .sup.3 PLA (Polylactic acid resin) = Mitsui Toatsu Chemicals LACEA H 100      MFR 13 190° C. 2.16 kg;                                                .sup.5 Polyester 1 = BASF ZK 242/108 copolyester of aliphatic diols and       aliphatic/aromatic dicarboxylic acids MVR 3.0 at 190° C./2.16 kg;      .sup.6 PCL (Polycaprolactone) + Union Carbide Tone Polymer P787 MFI 1.0       125° C. 44 psi g/10 min;                                               .sup.7 Extrusion Equipment = Werner & Pfleiderer ZSK 40;                      *0.1-0.4% water content                                                  

EXPERIMENT EXAMPLE 29

In analogy to experiment 28, the polyesteramide BAK 1095 was in example29 compounded with 10% potato starch in the twin-screw extruder ZSK 40at 155° C. and 20 bar with removal of water, extruded with 0.15%residual moisture, and, after the polyester extrudate had cooled, wasgranulated. The polymer mixture has an MFI g/10' of 25 at 150° C./5 kgand is suitable for producing blown and flat films.

Injection moldings, extrudates and films produced by means of polymermixtures proposed in accordance with the invention have not onlyrelatively good material properties but also an outstanding biologicaldegradability, which is why they are able to make a significantcontribution to the acute problem of waste. For example, films producedfrom a polymer mixture proposed in accordance with the invention areoutstandingly suitable for a very wide variety of applications in theagricultural sector, for example for the covering of fields, since suchfilms after their use can either be composted or else ploughed into theearth in the field. Polymer mixtures of this kind are also suitable forthe production of composting sacks, containers for composting waste,etc. In addition, containers and bottles, for example, can be producedfrom the polymer mixture proposed in accordance with the invention bymeans of blow molding.

The polymer mixtures according to the invention are also suitable,however, for the production of textile articles, for example for theproduction of fibers, monofilaments, sheetlike structures, such aswovens, felts, nonwovens, so-called backsheets, textile composites,flocks, wadding, and linear structures, for example filaments, yarns,cables, cords, etc. In particular it has been found in practice that thepolymer mixtures according to the invention are suitable for theproduction of sanitary articles, such as diapers, sanitary towels,incontinence products and bed liners. The structure of these hygienearticles includes, inter alia, nonwovens produced from the polymermaterial according to the invention, since this material has a very goodskin compatibility, is respiratorily active, is permeable to water vaporat the same time as being watertight, and yet is fully biologicallydegradable.

A large proportion of the polymer mixtures proposed in accordance withthe invention, especially those containing thermoplastic starch and/or acopolyester and/or a polyesteramide and/or a polyesterurethane, aresuitable, moreover, as adhesives or else can be used as coatings, forexample for the impregnation of textile wovens. In this case it has beenfound that the polymer mixtures proposed in accordance with theinvention which are suitable for these areas of application areintroduced and applied preferably in a form in which they are at leastpartially dissolved in alcoholic solvents. For example, in connectionwith experiment example 29 it was found, surprisingly, that the polymermixture thus prepared is soluble in hot alcohol/ethanol mixture. A 20%strength alcoholic solution directly after preparation has a viscosityof 100^(m) Pas. In this case too there was a possible use in the contextof a biologically degradable adhesive, as a coating or as animpregnation which brings about hydrophobic properties and is permeableto water vapor. The use ascertained with regard to experiment example 29can also be transferred to a large number of the other experimentexamples and to further polymer mixtures proposed in accordance with theinvention.

The polymer mixtures according to the invention are, however, of coursesuitable for umpteen other applications, for example for disposableinjection-molded products, etc.

We claim:
 1. A composition of matter that is at least partiallybiodegradable comprising:thermoplastic starch formed by mixing starchand at least one plasticizing agent under conditions that result in theformation of a thermoplastic melt so that the thermoplastic melt has awater content of less than 5% while in a melted state, wherein theplasticizing agent is selected from the group consisting of glycerin,sorbitol, sugar alcohols, hydroxy acids, playvinyl alcohol, and mixturesthereof; and at least one polymer selected from the group consisting ofaromatic polyesters, polyester copolymers having both aliphatic andaromatic blocks, polyester amides, polyethylene oxide polymers,polyglycols, and polyester urethanes, wherein the composition is formedby melting and mixing the thermoplastic starch and the at least onepolymer under conditions that reduce or maintain the water content ofthe composition at less than about 1% by weight while in a melted state.2. A composition of matter as defined in claim 1 formed by melting andmixing the thermoplastic starch and the at least one polymer underconditions that reduce or maintain the water content of the compositionat less than about 0.5% by weight while in a melted state.
 3. Acomposition of matter as defined in claim 1 formed by melting and mixingthe thermoplastic starch and the at least one polymer in a manner so asto reduce or maintain the water content of the composition at less thanabout 0.1% by weight while in a melted state.
 4. A composition of matteras defined in claim 1, wherein the polymer comprises a polyestercopolymer of at least one polyol and at least one aromatic dicarboxylicacid.
 5. A composition of matter as defined in claim 4, wherein thepolyol is selected the group consisting of 1,2-ethanediol,1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and mixtures thereof,and wherein the aromatic dicarboxylic acid is a terephthalate and,optionally, adipic acid or sebacic acid or both.
 6. A composition ofmatter as defined in claim 1, wherein the polymer is a polyestercopolymer of at least one polyol, at least one aromatic dicarboxylicacid and at least one aliphatic dicarboxylic acid.
 7. A composition ofmatter as defined in claim 6, wherein the polyester copolymer is apolyalkylene terephthalate.
 8. A composition of matter as defined inclaim 1, further comprising at least one aliphatic polyester orcopolyester.
 9. A composition of matter as defined in claim 8, whereinthe aliphatic polyester or copolyester comprises polycaprolactone.
 10. Acomposition of matter as defined in claim 1, further comprising at leastone additional component selected from the group consisting ofadditional plasticizers, stabilizers, antiflaming agents, additionalbiologically degradable biopolymers, organic fillers, and cross-linkingagents.
 11. A composition of matter as defined in claim 1, wherein thethermoplastic starch is included in an amount in a range from about 10%to about 95% by weight of the composition.
 12. A composition of matteras defined in claim 1, wherein the thermoplastic starch is included inan amount in a range from about 30% to about 65% by weight of thecomposition.
 13. A composition of matter as defined in claim 1, furthercomprising at least one additional polymer selected from the groupconsisting of ethylene/acrylic acid copolymer and ethylene/vinyl alcoholcopolymer.
 14. A composition of matter as defined in claim 1, whereinthe composition is formed by mixing and melting the thermoplastic starchand the at least one polymer at a temperature in a range from about 120°C. to about 260° C.
 15. A composition of matter as defined in claim 1,wherein the composition is formed by melting and mixing thethermoplastic starch and the at least one polymer in an extruder orkneader and wherein the composition is discharged from the extruder orkneader while in a melted state and subsequently cooled to asubstantially solidified state and conditioned so as to reabsorb water.16. A composition of matter as defined in claim 15, wherein thecomposition is conditioned so as to include a water content in a rangefrom about 1% to about 6% by weight of the substantially solidifiedcomposition.
 17. A composition of matter as defined in claim 15, whereinthe conditioned composition is in the form of a granulate.
 18. Acomposition of matter as defined in claim 15, wherein the composition isconditioned so as to include a water content in a range from about 3% toabout 5% water by weight of the substantially solidified composition.19. A composition of matter as defined in claim 1, wherein thethermoplastic starch is formed from starch that has been initiallypredried to below its natural water content.
 20. A composition of matteras defined in claim 1, wherein the thermoplastic starch is formed fromstarch that initially includes its natural water content, wherein thenatural water content of the starch is reduced while the thermoplasticstarch is in a melted state.
 21. A composition of matter that is atleast partially biodegradable comprising:thermoplastic starch formed bymixing starch and at least one plasticizing agent under conditions thatresult in the formation of a thermoplastic melt so that thethermoplastic melt has a water content of less than 5% while in a meltedstate, wherein the plasticizing agent is selected from the groupconsisting of glycerin, sorbitol, sugar alcohols, and mixtures thereof;and at least one polymer selected from the group consisting of aromaticpolyesters, polyester copolymers having both aliphatic and aromaticblocks, polyester amides, polyethylene oxide polymers, polyglycols, andpolyester urethanes, wherein the composition is formed by melting andmixing the thermoplastic starch and the at least one polymer underconditions that reduce or maintain the water content of the compositionat less than about 1% by weight while in a melted state.
 22. Acomposition of matter as defined in claim 21, wherein the thermoplasticstarch is formed from starch that has been initially predried to belowits natural water content.
 23. A composition of matter as defined inclaim 21, wherein the thermoplastic starch is formed from starch thatinitially includes its natural water content, wherein the natural watercontent of the starch is reduced while the thermoplastic starch is in amelted state.
 24. A composition of matter that is at least partiallybiodegradable comprising:thermoplastic starch formed by mixing starchand at least one plasticizing agent under conditions that result in theformation of a thermoplastic melt so that the thermoplastic melt has awater content of less than 5% while in a melted state, wherein theplasticizing agent is selected from the group consisting of glycerin,sorbitol, sugar alcohols, hydroxy acids, polyvinyl alcohol, and mixturesthereof; at least one polymer selected from the group consisting ofaromatic polyesters, polyester copolymers having both aliphatic andaromatic blocks, polyester amides, polyethylene oxide polymers,polyglycols, and polyester urethanes; and a phase mediator comprising atleast one condensation reaction product of the thermoplastic starch andthe at least one polymer, wherein the composition is formed by meltingand mixing the thermoplastic starch and the at least one polymer underconditions that reduce or maintain the water content of the compositionat less than about 1% by weight while in a melted state.
 25. Acomposition of matter as declined in claim 24, wherein the thermoplasticstarch is formed from starch that has been initially predried to belowits natural water content.
 26. A composition of matter as defined inclaim 24, wherein the thermoplastic starch is formed from starch thatinitially includes its natural water content, wherein the natural watercontent of the starch is reduced while the thermoplastic starch is in amelted state.
 27. A composition of matter as defined in claim 24,wherein the composition, after being mixed and melted, is cooled withwater so as to substantially solidify the composition and allowed toreabsorb water so that the substantially solidified composition has awater content in a range from about 1% to about 6% by weight.
 28. Acomposition of matter that is at least partially biodegradablecomprising:thermoplastic starch formed by mixing starch an at least oneplasticizing agent under conditions that result in the formation of athermoplastic melt so that the thermoplastic melt has a water content ofless than 5% while in a melted state, wherein the plasticizing agent isselected from the group consisting of glycerin, sorbitol, sugaralcohols, hydroxy acids, polyvinyl alcohol, and mixtures thereof; and atleast one polyesters copolymer having both aliphatic and aromaticblocks, wherein the composition is formed by first melting and mixingthe thermoplastic starch and the at least one polymer under conditionsthat reduce or maintain the water content of the composition at lessthan about 1% by weight while in a melted state, followed by cooling themelted composition with water in order to substantially solidify thecomposition and allowing it to reabsorb water so that the substantiallysolidified composition has a final water content in a range from about1% to about 6% by weight.
 29. A composition of matter as defined inclaim 27, wherein the thermoplastic starch is formed from starch thathas been initially predried to below its natural water content.
 30. Acomposition of matter as defined in claim 27, wherein the thermoplasticstarch is formed from starch that initially includes its natural watercontent, wherein the natural water content of the starch is reducedwhile the thermoplastic starch is in a melted state.